The broad objective of this proposal is twofold--a study of formation of neuronal connections during development, and a study of synaptic function. Both areas are related to short and long-term interactions between neurons. A normal area of interaction in nerve cells is at the synapse, this being the reason for proposing to study both processes simultaneously. The study will help in understanding the pathology of neuron-target interactions. The discovery of the molecular mechanisms by which chains of neurons are organized and function in such a precise and reproducible pattern is central to the knowledge of the function of the vertebrate brain. The experiments will be performed in a simple avian neuroeffector system, which consists of central neuron in the accessory nucleus of the brain, the connecting cells in the ciliary ganglion, and its effector organs in the eye. The research will be centered on the pre and postsynaptic contacts, the interaction between these elements, and the modifications of these interactions by experimental manipulation of their central and peripheral connections. The work will be a joint effort involving electrophysiological, electron microscopic, histochemical and biochemical techniques. The experiments will be done in embryonic as well as mature cells, and they will be carried out in isolated superfused preparations and in tissue and organ cultures of the same elements.